Standing S Lock

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Standing S Lock


What’s a contractor to do when the width of a duct is larger than 2 ft but they still want to use Slip and Drive as the Transverse connection rather than moving to Ductmate (or TDC)? After all, without having to line up 4 Corners and gasketed frames for mating, the installation time using “Slip & Drive” method is much faster.

Standing S Lock allows contractor to use Slip & Drive method on Ductwork that otherwise would fall into TDC/F or Ductmate. Some contractors move away from Slip & Drive when the width of duct is 20″ or longer
Stack of Standing S Lock

This is where the Standing S Lock enters the picture. It’s basically a Flat S Lock with a 1” tall standing seam that adds rigidity to duct and is installed the same way Flat S Lock—on the top and bottom widths of the connection while still using the drive cleat on the shorter dimensions (the 2 sides of the duct).

SMACNA approves Standing S Lock for any width span when it’s a Low Pressure duct Job. On Medium pressure Duct jobs (3” wg)  it’s approved thru 36” wide Rectangular Duct. Contractors will vary on the Duct size they choose to use it on in place of Flat S; some will change over from Flat S to Standing S on 18” simply because it adds a stiffener to the Duct. This oftentimes allows them to connect the duct on the ground rather than in the air like they are forced to do on Flat S because it sags when lifting otherwise.

The main gauge is 24 ga followed by 26 ga and 22 ga.

This shop uses Flat S up to 16” and then at 18” moves to Standing S. Shop cuts to size and bundles for field crew
A Sheet Metal Contractor’s Duct Shop will often cut the 10 ft lengths of Standing S lock to the 8 or so common duct widths, bundle and store in a cubby; this provides a valuable service to their field crew. The cut length is 3/4” shorter than the Duct Width. For 24” wide Duct, the field would grab a bundle of the 23-1/4” length